Study on the ultra-high-frequency sensors for PD detection in power transformer

The traditional PD detection methods could not meet the requirement of PD detection for power transformers (especially for online monitoring), because of their narrow measuring band, poor anti-interference performance and less information. The ultra-high-frequency (UHF) PD detection method has been newly put forward. According to the detection experience in GIS and the discharge characteristics in power transformers, the authors have designed and developed a kind of UHF sensor, namely, the two-wire Archimedian planar spiral antenna. The effective frequency range of the sensor is 500-1500 MHz. The characteristics of this sensor are analyzed by antenna theory and measured in the laboratory, and it is shown that the sensor has superior performance characteristics. In this paper, the sensor is also applied to measure PD signals in transformer oil, and results show that it can be used to detect UHF PD signals in an effective frequency band, which is very useful for laying foundations on setting UHF PD detection in power transformers.